Tentering machine



March 17, 1970 w. CUNNINGHAM ETA!- 3,

TENTERING MACHINE 3 Sheets-Sheet 1 Filed March 27 1968 INVE N ORS.

I r I I,

WALLACE CUNNINGHAM, ALEXA BY NDER SCLATER w. CUNNINGHAM Er AL 3 ,500,515

March 17, 1970 TENTERING MACHINE 3 Shee ts-Sheet 2 Filed March 27, 1968 ALEXANDER SCLATER ATTYS.

March 17, 1970 w. CUNNINGHAM ETAL 3,500,515.

TEN'IERING MACHINE 5 Sheets-Sheet 5 Filed March 27, 1968 F c I- lNvsN'rons', WALLACE CUNNINGHAM BY ALEXANDER SCLATER ATTYS.

United States Patent 3,500,515 TENTERING MACHINE Wallace Cunningham and Alexander Sclater, Renfrewshire, England, assignors t0 Proctor & Schwartz, Inc., Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 27, 1968, Ser. No. 716,422 Int. Cl. D06c 3/02, 3/10; B29

U.S. Cl. 26-61 9 Claims ABSTRACT OF THE DISCLOSURE A tentering machine is provided wherein the clips thereof are vertically supported on runners which are inclined downwardly and inwardly toward the longitudinal center line of the machine, and are laterally supported by rollers bearing against a vertical track in horizontal alignment with the nip of the tenter clips. The clips are interconnected and advanced by a chain in vertical alignment with the line of nips of the tenter'clips.

The present invention relates to a tentering machine and has particular application to a tenter dryer for synthetic films which is designed to control the lateral elongation of the film during drying, or other heat treatment such as film orientation.

In conventional tenter dryers, a continuous length of Web material is conveyed through the dryer by tenter elements, either tenter clips or tenter pins, which engage the lateral marginal portions of the 'web and slide longitudinally through the dryer on chain rails along the opposite sides of the dryer housing. The two chain rails are mounted for transverse adjustment within predetermined limits so that they may be disposed parallel to one another or may be adjusted to converge or diverge at various angles, depending on the character of the Web material being dryed. When orienting synthetic films, the tentering machine is set to counteract any tendency of the film to shrink, and to stretch the web laterally as desired.

When tentering synthetic films, the web is normally held by tenter clips having a lower fixed jaw on a body slidable on the rail and secured to the chain, and an upper jaw pivotal between a closed clamping position in which it engages the fixed jaw, and an open position in which the web is released from engagement. The upper jaw has an operator which is actuated at the entrance end to clamp the jaw on the web material and at the exit end to release the web material.

A primary object of the present invention is to provide a tenter-clip-and-rail assembly which insures accurate control of the lateral stretching of the web material.

More particularly, the present invention provides a tenter clip having lateral support roller horizontally aligned with the point of engagement of the clip with the web material so as to provide a firm lateral support for the clip.

Another object of the present invention is to provide an assembly in which the tenter elements are interconnested by a chain which is in vertical alignment with the line of nips to thereby maintain the desired longitudinal spacing between the tenter elements at the points of nip precisely uniform.

More particularly, the present invention provides a novel assembly in which the chain rail has inner and outer walls forming an open-topped channel in which the chain travels, the tenter element sliding on the upper edges of the walls and having bearing or lateral thrust rollers bearing against a track on the outer surface of the' outer wall in horizontal alignment with the line of nip of the elements.

More specifically, the lateral thrust rollers comprise 3,500,515 Patented Mar. 17, 1970 upper and lower rollers rotatable about an upright axis, respectively above and below the level of the nip of the tenter element.

Even more specifically, the assembly provides runways on the tops of the inner and outer walls which are inclined downwardly and inwardly toward the center of the tentering machine in the operative run of the chain rail and are inclined downwardly and outwardly of the machine on the return run of the chain rail, so that the weight of the tentering elements on the runways urges the elements in a direction to cause the thrust rollers to bear against the track.

All of the objects of the invention are more fully set forth hereinafter with reference to the accompanying drawing wherein:

FIG. 1 is a transverse sectional view through one side of a tentering machine showing an assembly according to the invention with a tenter slip in the operative run of the chain rail in elevation and a tenter clip in the return run in section;

FIG. 2 is a sectional view similar to FIG. 1 illustrating an alternate embodiment of the assembly;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 1; and

FIG. 4 is a sectional view taken on the line 4-4 of FIG. 2.

Referring now to the drawing, the tenter assembly illustrated therein comprises a chain rail 12 extending along the longitudinal edges of a tentering machine for angular adjustment in conventional manner. The rail 12 mounts a series of tenter elements, in the present instance tenter clips 15, carrying an endless chain 14. The operative run of the chain is shown at 14a and the return run is shown at 1417. The chain rail 12 is formed with channels 18 and 19 for receiving the chain 14 in its operative and return runs, respectively. The channel 18 is formed by an upstanding inner wall 21 and an outer wall 22 spaced from the longitudinal center line of the chain rail 12, to form a roller trackway 23. A wearplate or roller track 24 is mounted on the vertical outer surface of the outer wall 22 to accept the inward thrust of the tenter clip 15. The trackway 23 is partially closed by an upstanding central partition 25 having an outwardly extending flange 26 at its upper end. The return channel 19 i formed identically so that the chain rail 12 is symmetrical about its longitudinal center line.

The tenter clips 15 are adapted to slide along the chain rail 12 supporting the chain 14 in the channels 18 and 19. The chain 14 is of conventional construction, including rollers 28 and links 29 iterconnected by roller pins 30. The chain is fastened to the clips 15 by suitable fasteners 27 to underlie the point of hip between the movable jaws 34 and the body portions 33. In this manner, when the chain makes a turn, as when entering the stretching zone, the longitudinal spacing between nips on adjacent clips is not substantially changed and there is no possibility of the film web W splitting due to longitudinal stretch between adjacent clips.

To provide smooth sliding movement of the clips 15, the upper surfaces of the walls 21 and 22 are formed as runways 31 and 32, respectively. The tenter clip 15 comprises a body portion 33 pivotally mounting a clamp 34 in a conventional manner. Runners 35 and 36, respectively, are provided on the body 33 to register with the runways 31 and 32, respectively. The runners comprise pads of hard, wear-resistant material affording smooth sliding movement of the clip on the runways 31 and 32. As shown at the left hand side of FIG. 1, when the clip is unloaded, the weight of the chain 14 is carried by the clip 15 with the pads 35 and 36 substantially equally supporting the load.

Inasmuch as the runways 31 and 32 are coplanar and inclined downwardly away from the center line of the chain rail 12, the clips 15 are thrust away from the center line of the chain rail. Thurst rollers are provided on the clip to accept this lateral thrust. To this end a roller assembly 41 is mounted on the body 33 beyond the runner 36 to depend downwardly into the trackway 23. In this embodiment of the invention, the roller assembly 41 includes a yoke 42 mounting a pair of roller shafts 43 and 44 (see FIG. 3). Upper rollers 45 and lower rollers 46 are rotatably mounted on the shafts 43 and 44 by suit- ,able anti-friction bearings so as to be freely rotatable by engagement with the track 24 as the clip 15 travels along the rail. Grease fittings are provided at 47 to insure lubrication of the anti-friction bearings.

' In the preferred embodiments of the invention, the angle between the plane of the runways 31 and 32 and the track 24 is less than the angle between the runners 35 and 36 and the axes of the roller shafts 43 and 44. In the idle position in the return run, where the runners 35 and 36 support the clip 15, the shafts 43 and 44 are inclined relative to the track 24 so that only the upper rollers 45 engage against the track. However, when the clip is under load in the operative run, the lateral force exerten by the web W material lifts the inner, pad 35 from the runway 31 and causes both the upper and the lower rollers 45 and 46, respectively, to bear against the track 24 to accept the lateral thrust. To accommodate the rocking movement of the shafts 43 and 44, the rollers have convex outer faces as shown. Furthermore, the corner of the pad 36 closest to the trackway 23 is bevelled as indicated at 36a.

By reason of the freedom for rocking movement, the clip accommodates itself to the different conditions which exist respectively in the loaded and unloaded positions. In the loaded position when the lateral thrust of the clip is at a maximum, both the upper and the lower rollers accept the full thrust and the sliding friction between the runners and the runway is reduced to a minimum, thereby providing primarily rolling friction which affords relatively smooth operation. It should be noted that the upper and lower rollers 45 and 46 are disposed respectively above and below the extended plane of the webmaterial W; in this manner the thrust is substantially equally divided between the upper and lower rollers to provide substantially even wear thereon. In the return run, when the lateral thrust is at a minimum, the thrust on the lower rollers 46 is eliminated so that the entire thrust is concentrated against the upper rollers. The confinement of the thrust to the upper rollers insures firm engagement ofthese rollers against the track and provides suflicient force to insure rolling movement of the rollers on their shafts, avoiding the possibility of uneven wear or flats due to non-rolling.

To insure against inadvertent displacement of the tenter clips from the trackway 23, the terminus of the body portion 33 closest to the center-line of the rail 25 is cutout as indicated at 38 to provide a recess having a shoulder 39 which engages under the flange 26. In the event of excess loading by the film web W, both runners 35 and 36 may disengage the runways 31 and 32, eliminating allsliding friction between the clip and the chain rail. Upward disengagement of the rollers 45 and 46 from the track 24 is prevented by the flange 26 engaging the shoulder 39. In this manner, with the roller assembly 41-- retained in the trackway 23 by engagement of the shoulder 39 under the flange 26, the clip is constrained to travel on the runways 31 and 32.

The confinement of the roller assembly within the trackway 23 provides the advantage of positioning the thrust-accepting members of the tenter clip substantially remote from the web W being tentered, so that in the event of dirt, grea or other particles being flung from the rollers, the trackway 23 confines these particles and protects the film web W from d m ge ther by- By the 4 same token, the chain 14 is confined in the channels 18 and 19 so as to limit the possibility of dirt or grease from the chain engaging the web. In order to further limit the possibility of dirt being blown against the web by the blow nozzles, a deflector plate is provided at the inner side of the chain rail as indicated at 50.

The return channel 19 with the return run 14b of the chain may be enclosed in a suitable insulated housing 51 mounted to overlie the channel 19 and the trackway 23. In addition a web shield 52 may project outwardly 'over the clips 15 in the operative run. In the illustrated form, the chain rail 12 has a central recess 53 in which may be mounted suitable heat exchangers for controlling the temperature of the rail 12 and thereby avoid the adverse effects of substantial temperature gradients during the operation of the tentering machine.

In the embodiment of FIGS. 2 and 4, the parts are identical with the exception of the roller assembly and its mounting on the tenter member. In this embodiment the roller assembly 141 comprises a single upper roller 145 and a single lower roller 146, both of substantially greater diameter than the rollers 45 and 46. The rollers are mounted on shafts 143 and 144 anchored in the extended body of the tenter clip 115, and having spacer plates 147, 148, and 149. The roller assembly 141 has particular utility when stretching lightweight film, inasmuch as in such applications, the weight of the clip is a substantial factor. The use of two rollers instead of four in the roller assembly substantially reduces the weight of the tenter member without substantially affecting the desired functional characteristics set forth above.

Other modifications may be incorporated in the assembly of the present invention. For example, the runners of the clip may incorporate anti-friction means of suitable form, reducing the need for the permitting rocking movemnt of the clip between the loaded and the unloaded positions.

While particular embodiments of the invention have been illustrated and described herein, it is not intended to limit the invention to such disclosures, but changes and modifications may be made therein and thereto without departure from the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a tentering machine for web material having a series of tenter elements carrying a tenter chain, and a chain rail having inner and outer walls defining therebetween a channel adapted to receive the tenter chain therein for longitudinal movement and having an upright track on the outer side of the outer wall; the improvements wherein said tenter elements overlie said inner and outer walls and have runner means engageable with the upper ends of said walls so as to support the chain therebetween in said channel; wherein further each of said clips extends beyond said outer wall and mounts a downwardly depending roller assembly, said downwardly depending roller assembly including upper and lower rollers each mounted for rotation about an upright axis in said assembly and engageable with said track; and wherein further each tenter element has a nip for engaging the web material disposed in a horizontal plane and adapted to exert a horizontal thrust on said element, said upper and lower rollers being positioned respectively above and below the horizontal plane including said nip, said nip being in vertical registry with said chain.

2. An assembly according to claim 1 in which said roller assembly includes two upright roller shafts spaced longitudinally of said rail, said upper roller being mounted for rotation on one of said shafts and said lower roller being mounted for rotation on the other of said shafts.

4. An assembly according to claim 3 wherein the angle between said runway-plane and said track is less than the angle between said runner-means and the axis of said rollers, whereby said clip is free to rock between one limit position wherein said runner-means both engage said runways and the upper roller engages said track; and a second position wherein both of said rollers engage said track and the runner-means engages only the outer wall runway.

5. An assembly according to claim 4 wherein said runner-means comprises a pair of pads mounted on each of said elements, respectively in vertical registry with said walls, the pad overlying the outer wall being bevelled at its outer end nearest the track so as to facilitate rocking of the clip.

6. An assembly according to claim 4 wherein the rollers have convex outer faces.

7. An assembly according to claim 1 wherein said outer wall terminates above the level of the horizontal plane of said nip, and the inner wall terminates below said horizontal plane.

8. For use in a tentering machine having a chain rail extending longitudinally along one side thereof with a pair of laterally-spaced longitudinal runways, a tenter clip comprising a body and an upper jaw pivoted to said body for operation between a closed nipping position and an open position; and a chain adapted to travel longitudinally of said rail intermediate said runways; said body having runner means on its underside adapted to engage and travel on said runways, fasteners for securing said chain to said body intermediate said runner means in a position substantially underlying the nip of said upper jaw with said body, and a thrust roller assembly having upright runner-means comprises a pair of pads on the underside of said clip, one of said pads being positioned above said horizontal plane and the other of said pads being positioned below said horizontal plane, the upper pad being adjacent said rollers.

References Cited UNITED STATES PATENTS 670,598 3/ 1901 Rusden. 2,799,913 7/1957 Mohring et a1. 2,945,280 7/1960 Liebert. 3,118,212 1/ 1964 Parkinson.

FOREIGN PATENTS 112,553 1/ 1918 Great Britain.

549,075 10/ 6 Italy.

OTHER REFERENCES German printed application 1,056,570, May 1959.

ROBERT R. MACKEY, Primary Examiner US. Cl. X.R. 18-1; 2662 

